The majority of states require brakes on all but the smallest of trailers. To meet this requirement electric brakes, operated by the twelve volt electrical system of the tow vehicle, have been used on trailers for several years. The electric brake system of the trailer is integrally connected with the brake and electrical systems of the tow vehicle by a controller which transforms pressure from the master cylinder of the tow vehicle or deceleration of the tow vehicle into electrical current. In general, once hydraulic pressure within the brake system of the tow vehicle or deceleration reaches a selected level, electric current is allowed to flow to the electric brakes of the trailer, thereby effecting braking.
As electric drum brakes rely on an electromagnet to convert the electrical energy supplied by the controller to mechanical energy, the safety and reliability of the brakes depend on the effectiveness of the electromagnet. Typically, the electromagnet will be mounted on an outwardly projecting tang of an actuating lever within the electric drum brake. In this normal mounting method, the magnet experiences metal to metal contact with the tang. Thus under normal operating conditions, road vibrations subject the electromagnets to severe stress. After several miles, the magnet and supporting tang suffer extreme wear which in some cases can result in total failure of the brake unit.